Diversity for a new install

63 amps per unit sounds reasonable if they are to be all electric.

But that does not mean that the total demand will be 63 amps for each unit at the same time.

When calculating transformer size and the like, the DNOs allow about 10 amps per all electric dwelling for large numbers of homes. If calculated on that basis, then for 200 units you need about 2,000 amps, and 800 amps per phase would probably suffice.

To a large extent it depends on the pattern of use. If by "holiday home park" it is intended primarily for fine weather use, then about 10 amps per unit is reasonable.

If however these cabins are to become full time homes, all with electric heating, then on a cold winter day 800 amps per phase might prove insufficient. Especially if electric cars become popular.

Whilst the DNOs allow about 10 amps per home if mains gas is not available, this presumes that some houses will use bottled gas, oil, or solid fuel for heating.  If use of these fuels is not expected, then winter demand might reach 20 amps per unit. Say an average of a couple of 2 kw heaters and a few hundred watts for lighting and small appliances.

The other risk is that all the holiday cabins might be let not to random holiday makers, but to persons all attending some large political, religous, or cultural event. That can tend to increase maximum demand if large numbers all arrive at the same time and turn on heaters.

Ultimately it comes down to engineering judgement and some knowledge of expected use. Is the electricity to be metered, or included in the rent ? If included it will be used far more liberally.

A suburban housing estate of 200 homes might have two or three empty and for sale, and another half a dozen empty due to holidays. So about 5% consuming almost nothing. 200 holiday homes could well have every single unit used at the same time.

Cables will almost certainly be sized for voltage drop rather than for current carrying capacity.

63 amps per unit sounds reasonable if they are to be all electric.

But that does not mean that the total demand will be 63 amps for each unit at the same time.

When calculating transformer size and the like, the DNOs allow about 10 amps per all electric dwelling for large numbers of homes. If calculated on that basis, then for 200 units you need about 2,000 amps, and 800 amps per phase would probably suffice.

To a large extent it depends on the pattern of use. If by "holiday home park" it is intended primarily for fine weather use, then about 10 amps per unit is reasonable.

If however these cabins are to become full time homes, all with electric heating, then on a cold winter day 800 amps per phase might prove insufficient. Especially if electric cars become popular.

Whilst the DNOs allow about 10 amps per home if mains gas is not available, this presumes that some houses will use bottled gas, oil, or solid fuel for heating.  If use of these fuels is not expected, then winter demand might reach 20 amps per unit. Say an average of a couple of 2 kw heaters and a few hundred watts for lighting and small appliances.

The other risk is that all the holiday cabins might be let not to random holiday makers, but to persons all attending some large political, religous, or cultural event. That can tend to increase maximum demand if large numbers all arrive at the same time and turn on heaters.

Ultimately it comes down to engineering judgement and some knowledge of expected use. Is the electricity to be metered, or included in the rent ? If included it will be used far more liberally.

A suburban housing estate of 200 homes might have two or three empty and for sale, and another half a dozen empty due to holidays. So about 5% consuming almost nothing. 200 holiday homes could well have every single unit used at the same time.

Cables will almost certainly be sized for voltage drop rather than for current carrying capacity.